1. Field of Invention
The present invention relates to a desulfurization method of a nitrogen oxide absorption catalyst system. More particularly, the present invention relates to a desulfurization method of a nitrogen oxide absorption catalyst system that is poisoned by sulfur that is included in a diesel fuel.
2. Description of Related Art
Generally, a Lean NOx Trap (LNT) of a diesel engine absorbs NOx of exhaust gas in a condition and uses a rich condition of fuel to reduce NOx to N2 and O2 when the abosorbed NOx reaches a maximum capacity.
The LNT catalyst is poisoned by sulfur element included in the fuel and the performance thereof is deteriorated. The engine driving condition is varied so as to eliminate the poisoned sulfur of the LNT, wherein the exhaust gas is heated and simultaneously the real air/fuel ratio is adjusted. The real air/fuel ratio is adjusted to raise the temperature of the exhaust gas.
A conventional desulfurization method in a LNT system using a high sulfur diesel fuel calculates SOx amount of the LNT catalyst, determines a deterioration rate of the LNT catalyst according to the SOx amount, and determines the desulfurization timing.
Particularly, when the high sulfur diesel fuel having at least 100 ppm sulfur is used, the LNT catalyst is poisoned by the sulfur of the diesel fuel and the purification rate for NOx is deteriorated.
Here, the sulfur amount that is poisoned in the LNT and the sulfur amount that is slipped from the LNT are determined, and the desulfurization method is not simple, because the desulfurization control is operated by considering the particulate matters (PM) trapping condition of a diesel particulate filter (DPF).
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.